1. Field of the Invention
The present invention relates to an exposure meter circuit of the camera with a matching network for flash device and particularly to an exposure meter circuit of the camera with matchability with the detecting network for detecting the quantity of flashlight automatically.
2. Description of the Prior Art
When the so called speed light device is used as a flash device, conventionally the electrical energy for flash is stored in the condensor in advance and by means of the synchronizing flash signal from the camera side, the stored energy is converted into the energy of light (for example, in a Xenon tube) so as to obtain an auxiliary illumination.
In case of such speed light device, the quantity of flashlight is set according to the energy charged in the condensor so that it is essential to charge the condensor always up to a certain determined level in order to obtain a certain determined quantity of light. Therefore the determined light quantity cannot be obtained when the speed light device operates while the level of the stored energy is lowered due to the consumption of the current source or before the condensor has been fully charged, which is disadvantageous because proper auxiliary light photography cannot be carried out.
In order to eliminate the above mentioned disadvantage, a method has been proposed according to which the level of the stored energy in the flashlight device is always detected by means of a detecting network so as to control the exposure element such as a diaphragm device on the camera side in such a manner that a proper correction corresponding to the stored energy is always carried out on the exposure elements.
FIG. 1 and FIG. 2 respectively show a circuit of a flashlight device and a circuit of an exposure meter at the camera side, to be connected with the above mentioned circuit. In FIG. 1, 1 is a photoconductive element, 2 an ampere meter, 3 a cell, 4 the main switch, 5 the trigger contact for the flashlight device. In FIGS. 2, 6 is the cell, 7 to 11 compose an oscillation network for charging, in which 7 is a transistor, 8 and 9 condensors, 10 a coil and 11 a resistance for starting the oscillation. 12 are diodes, 13 the main condensor and 14 to 16 a trigger network, whereby 14 is a resistance, 15 a trigger condensor, 16 a trigger coil and 17 a discharge tube. 18 is a triple main switch for flash device. 19 to 30 compose a network automatic flashlight, whereby 19 is the resistance for transmitting the information of the distance of the object, 20 and 21 are the resistances for controlling the potential of the base of the transistor 28 so as to set the level of the output. 22 and 23 are the resistance for determining the light producing voltage of the neon tube 24. 25 is the resistance for determining the potential of the collector of the switching transistor, while 26 is the resistance for determining the characteristics between the distance of the object and the deflection angle of the ampere meter in the camera.
The transistors 27 and 28 and the resistance 29 and 30 indicate the elements for forming a detection circuit to detect the voltage which charges the main condenser 13. In order to connect the flashlight device (FIG. 2) with the camera (FIG. 1) A.sub.1 is connected with A.sub.2, B.sub.1 with B.sub.2, C.sub.1 with C.sub.2 and D.sub.1 with D.sub.2. In order to bring the automatic flashlight mechanism which uses the ampere meter in the camera into operation it is necessary to supply a voltage of + 1.3 V to the terminal B.sub.2 from the terminal D.sub.2. Further in order to connect the electrical network at the camera side with that of the flashlight device it is most rational to carry out the electrical connection by making the standard potential at the camera side match with that of the body of the flashlight device, because in this way the number of the electrical contacts between the camera and the flashlight device becomes minimum.
When however other exposure meter circuit than is shown in FIG. 1 is connected to the flashlight circuits shown in FIG. 2, the foregoing voltage of + 1.3 V from the terminal D.sub.2 is not applied to terminal B.sub.2, thus the detecting network consisting of 27 to 30 of the flashlight device does not operate effectively. Further the exposure meter circuit itself does not have the automatic flashlight function and in taking the energy storage quantity of the flashlight no effective function can be expected of the flashlight circuit, which is disadvantageous.